The inventive concept relates generally to frequency synthesizers. More particularly, the inventive concept relates frequency synthesizers that are immune to channel coding errors during course tuning, as well as methods controlling frequency synthesizers in such a manner that channel coding errors are avoided.
A frequency synthesizer is a device capable of generating a range of discrete output signals, each having a given frequency. The different frequencies generated by the frequency synthesizer are defined across a band of possible frequencies and may be separated by a constant frequency interval. Thus, a frequency synthesizer may be used to variably select a desired or target frequency from among a plurality of frequencies defined over a relatively wide band of frequencies.
To accomplish this selection and generation of an output signal having a target frequency, the frequency synthesizer may divide its relatively wide band of possible frequencies into a plurality of narrower frequency bands. These relatively narrow frequency bands may be distinguished from one another during a selection procedure in accordance with corresponding channel codes. Thus, when the frequency synthesizer is instructed (or controlled) to generate an output signal having a target frequency, it may first select a corresponding channel code that determines a narrow frequency band from among the plurality of narrow frequency bands that captures (or is closest to) the target frequency, and thereafter lock to the target frequency within the determined narrow frequency band.
However, when an errant channel code is determined during a first step of this two step process, the frequency synthesizer may thereafter be unable to properly lock the output signal to the target frequency—at least without recourse to some external error correction measures (e.g., external channel code error detection and correction circuitry) or a lengthy channel code search routine. Such outcomes greatly diminish the responsiveness of the frequency synthesizer and impair overall system performance.